Superhard material article of manufacture

ABSTRACT

The invention relates to abrasive water jet systems comprising an abrasive water jet mixing tube having a longitudinal bore lined with a superhard material, including such systems which use cubic boron carbide (CBN), diamond, or other materials with a hardness greater than that of alumina as the abrasive material. The invention also comprises methods of using an AWJ system having a mixing tube having a longitudinal bore lined with a superhard material. Some embodiments include AWJ mixing tubes comprised of a plurality of connected components. Such connections may be disconnectable.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation-in-part of currently pendingapplication No. 09/316,786 filed May 21, 1999.

FIELD OF THE INVENTION

[0002] The present invention relates to superhard articles ofmanufacture for use in many applications but preferably for use asmixing tubes for use in high-pressure abrasive water jet systems andmethods for producing same. More particularly, the invention relates tomixing tubes using a superhard material, i.e. PCD (polycrystallinediamond) or electrically conductive PCBN(polycrystalline cubic boronnitride), in high pressure abrasive water jet systems and methods forproducing same. The present invention also relates to abrasive water jetsystems comprising an abrasive water jet mixing tube having alongitudinal bore lined with a superhard material.

BACKGROUND OF THE INVENTION

[0003] High pressure abrasive water jet (AWJ) machining utilizes a verynarrow stream of high pressure water laden with abrasive particles toerosion cut through a workpiece. AWJ machining is used in manyindustries, including the automobile, aerospace, computer, and glassindustries, to create precision parts from a wide variety of materialssuch as plastics, metals, glass, composites, and ceramics, includingthose materials which are otherwise difficult to machine. The AWJprocess machines with high precision, very little kerf, and produces aclean, smooth edge thereby reducing or eliminating the need for costlypost-machining edge treatment operations. Because AWJ machining is a lowtemperature operation, it produces no heat affected zone in the machinedpart and can be used to machine heat treated parts without disturbingtheir heat treatment-induced material properties. AWJ machining headsmay be guided by hand, machine, or computer with the most precisemachining being obtained by computer-control of the AWJ machining headmotion.

[0004] In a typical AWJ system, an intensifier pump is used topressurize filtered water to the range of about 2,000 to 100,000 psi (14to 690 MPa). The high pressure water is fed into an AWJ machining headwhere it is forced to pass through a nozzle orifice diameter as small asa few thousands of an inch (a few hundredths of a millimeter) togenerate a high-velocity water jet. In commercial applications, abrasiveparticles such as garnet or olivine are introduced into thehigh-velocity water jet as it passes through a mixing chamber within theAWJ machining head. The abrasive particles and the high-velocity waterjet mix as they travel together through the small diameter longitudinalbore of a mixing tube in the AWJ machining head to form upon exiting themixing tube a narrow, abrasive, high-velocity water jet that is capableof making precise cuts through almost any kind of material.

[0005] An AWJ mixing tube longitudinal bore is subjected to severejetting abrasion from the high-velocity water jet and abrasive particlesit carries. However, the precision and the efficiency of AWJ machiningis greatly affected by wear of the longitudinal bore of the mixing tube.Although the longitudinal bore diameters generally are on the order of0.010 to 0.060 inches (0.25 to 1.5 mm) and the overall lengths of AWJmixing tubes are usually on the order of 2 to 4 inches (5 to 10 cm),longitudinal bore diameter erosion of just a few thousands of an inch (afew hundredths of a millimeter) can greatly reduce the machiningefficiency and degrade the machining precision, especially when thelongitudinal bore erosion is near the exit end of the mixing tube. AWJmixing tube longitudinal bore wear results in longer machining times,less precise machining, down time for replacing the worn mixing tube,and the cost of the replacement mixing tubes. To minimize this problem,AWJ mixing tubes are commonly made of a very hard materials, such astungsten carbide.

[0006] In the past, there have been efforts to improve the wearresistance of AWJ mixing tubes by using chemically vapor-deposited (CVD)diamond as a longitudinal bore lining material. Diamond is an allotropeof carbon exhibiting a crystallographic network comprising covalentlybonded, aliphatic sp³ hybridized carbon atoms arranged tetrahedrallywith a uniform distance of 1.545 Å (0.1545 nm) between atoms and isextremely hard, having a Mohs hardness of 10. For example, Banholzer etal, U.S. Pat. No. 5,363,556, estimates that the use of diamond canextend the useful lifetime of AWJ mixing tubes from the about two tofour hours obtained for conventional tungsten carbide mixing tubes toabout twenty to one hundred hours.

[0007] Banholzer et al., supra, describes a method of making a AWJmixing tube by depositing a diamond layer by CVD on a funnel shapedsupport member to form an inner member of diamond, separating the innermember from the support member, depositing an outer member materialhaving a higher coefficient of thermal expansion than diamond on anouter side of the inner member to form an outer member of the mixingtube, and cooling the mixing tube co contract the outer member forinducing compressive stresses of sufficient strength on the inner memberto substantially prevent the formation of cracks in the inner member.Anthony et al, U.S. Pat. No. 5,439,492, describes making a AWJ mixingtube by depositing a layer of diamond by CVD on a mandrel followed byremoving the mandrel mechanically or by chemical etching to form thelongitudinal bore of the mixing tube and then, optionally, providing asteel tube to support the diamond film. Stefanick et al., U.S. Pat. No.5,785,582, describes depositing a layer of diamond by CVD on opposingsides of the longitudinal bore of a AWJ mixing tube made of a hardceramic material that has been split longitudinally and then joining thetwo halves of the mixing tube together by shrink fitting a metal sheatharound them.

[0008] There also have been efforts to use other forms of diamond andmaterials having hardnesses approximating that of diamond. JapaneseUtility Model Application Laid-Open No. 63-50700, describes an AWJmixing tube comprising a plurality of dies built in a sleeve main body.Each die consists of a knob of a polycrystalline sintered body ofdiamond or cubic crystal boron nitride, or the like, which is fixed tothe inner circumference of an annular supporting stand metal of a toughmaterial such as a super-hard alloy, high-speed steel, or the like. Eachknob has a through-hole. However, the AWJ mixing tube described abovehas the disadvantage that wear occurs preferentially at the junctionareas between the dies (see Examined Japanese Utility ModelHEI-6-34936).

SUMMARY OF THE INVENTION

[0009] The inventors of the present invention have developed a method ofproducing an AWJ mixing tube with a longitudinal bore lined with asuperhard material which does not require the use of diamond depositedby CVD. The present invention comprises methods for making an AWJ mixingtube using one or more pieces of a superhard material. The term“superhard material” as used herein refers to polycrystalline diamond(PCD) or polycrystalline cubic boron nitride (PCBN) which can bemachined by electrical discharge machining (EDM). PCD is a particularspecies of synthetic diamond. PCD is produced by sintering together manyindividual diamond crystals in the presence of a catalyst at hightemperatures and pressures into a coherent mass of interbonded diamondcrystals. The catalyst may be provided in the form of a powderintermixed with the diamond crystals or it may be included in anadjacent element from which it infiltrates through the spaces betweenthe diamond crystals during the sintering process. For example, one waythe catalyst can be provided is by placing diamond grit on a substratecomprising a cemented tungsten carbide having 5-20 weight percent binderof cobalt or cobalt-nickel and then subjecting these components to hightemperatures and pressures so that a portion of the binder of thecemented tungsten carbide infiltrates the diamond grit and catalyzesdiamond to diamond bonding. Some of the binder (e.g. cobalt orcobalt-nickel) is left in the PCD.

[0010] PCBN, which is sufficiently electrically conductive to be EDMmachined, may be used in the present invention as a superhard materialfor lining in the AWJ mixing tube longitudinal bore. PCBN may beproduced in a manner similar to that used for producing PCD.

[0011] A particular advantage of PCD over other types of diamond is itsability co be machined by EDM due to its electrically conductivemetallic content. The present invention takes advantage of thischaracteristic and comprises a method of producing an AWJ mixing tubehaving a longitudinal bore lined with a superhard material, the methodcomprising the steps of providing at least one superhard material bodyand then EDM machining the at least one superhard material body to formthe longitudinal bore of the AWJ mixing tube. Preferably, the presentinvention includes providing the longitudinal bore with a taperedentryway by EDM machining so as to facilitate the entry of the highvelocity water jet and the abrasive grit into the AWJ mixing tubelongitudinal bore. Also according to the present invention, anynecessary machining of the external dimensions of the superhardmaterial-cored AWJ mixing tube such as, for example, to permit themixing tube to fit into an AWJ machining head or to provide desirableexternal features such as an exit end taper, is done prior to,concurrently with or subsequent to the machining of the mixing tubelongitudinal bore. used herein, the “flow passage” of an AWJ mixing tubeis the conduit which extends from one end of the mixing tube to theother through which the high velocity water jet and abrasive grit enter,travel through, and exit the mixing tube. The flow passage includes alongitudinal bore and may also include a tapered entryway. However, whenthe term “flow passage” is used in describing a single component of anAWJ mixing tube, the term refers to the conduit that extends from oneend of the component to the other through which the high velocity waterjet and abrasive grit enter, travel through, and exit the component. Asused herein, the term “component” refers to a discrete, hollow segmentcomprising a portion of the length of an AWJ mixing tube; components areconnected together to form a multi-component AWJ mixing tube.

[0012] As used herein, the term “flow-through direction” is thedirection the high velocity water jet and abrasive grit travel throughthe AWJ mixing tube.

[0013] The present invention includes AWJ mixing tubes having asuperhard material lining at least part of the AWJ mixing tube's flowpassage. Such AWJ mixing tubes comprise a superhard material lining atleast a part of at least one of the tapered entryway and thelongitudinal bore of the AWJ mixing tube. In some embodiments, asuperhard material lines the entire length of the longitudinal boreand/or the tapered entryway. In other embodiments, a superhard materiallines only part of the longitudinal bore length and/or the taperedentryway while the rest of the longitudinal bore length and/or taperedentryway is lined with another type of abrasion-resistant material. Thepart or parts of the flow passage of the AWJ mixing tube which are to belined with superhard material rather than some other type ofabrasion-resistant material are those part or parts which the user ofthe AWJ mixing tube desires most to protect from erosion during use.

[0014] Although the present invention includes methods for producing AWJmixing tubes which are comprised solely of a superhard material, it alsoincludes methods for producing AWJ mixing tubes in which the superhardmaterial is surrounded substantially along the length of the mixing tubewith a durable material which can act to reduce the susceptibility ofthe mixing tube to damage from external forces or to facilitate theadaptation of the superhard material into the AWJ machining head. Thedurable material may also function to reinforce the superhard materialso as to prevent the AWJ mixing tube from being damaged by water jetback pressure should the mixing tube become plugged during operation.The present invention also includes methods for producing AWJ mixingtubes which comprise at least one jacket which acts to reduce thesusceptibility of the AWJ mixing tube from impact damage or tofacilitate the adaptation of the AWJ mixing tube into the AWJ machininghead.

[0015] Accordingly, the present invention also comprises the steps ofsurrounding at least one superhard material body substantially along thelength of the AWJ mixing tube with a durable material. In oneembodiment, in the completed AWJ mixing tube, the durable material willextend beyond the superhard material at the entrance end of the mixingtube with a tapered entryway portion of the mixing tube being formed atleast partially in the durable material and the method of the presentinvention includes forming the mixing tube in this fashion. The durablematerial is preferably a steel or, more preferably, a cemented tungstencarbide. When the tapered entryway is formed at least partially in thedurable material and the durable material is a steel, it is desirablethat the steel be an erosion-resistant alloy steel or tool steel.

[0016] When cemented tungsten carbide is used as the durable material,in the above one embodiment of the present invention includes the stepsof (1) providing at least one composite body comprising a superhardmaterial layer bonded to a cemented tungsten carbide substrate; (2)providing at least one durable material body; (3) bonding the at leastone composite body to the at least one durable material body so as toform an AWJ mixing tube blank having a superhard material core; (4) EDMforming a tapered entryway into one end of the AWJ mixing tube blank;and (5) EDM machining a longitudinal bore through the superhard materialcore of the AWJ mixing tube blank. The method may further comprise thestep of machining the external shape of the AWJ mixing tube blank in oneor more operations to adapt the AWJ mixing cube blank to fit into an AWJwater jet machining head and to otherwise obtain the final dimensions ofthe AJW mixing tube. Note that the term “AWJ mixing tube blank” is usedherein to refer to a single body, whether of a monolithic or a compositeconstruction, from which an AWJ mixing tube may be formed in one or moreoperations and includes partially formed AWJ mixing tubes up until thelast forming operation has been completed.

[0017] In this embodiment, the durable material body is provided as asingle round rod having a unshaped channel adapted for receiving the atleast one strip of composite material. However, the present inventionalso includes providing the durable material in other shapes. Thepresent invention also includes providing a plurality of durablematerial bodies which can surround and be bonded to the one or moresuperhard material bodies. What is important is that the resulting AJWmixing tube blank have a superhard material core into which alongitudinal bore may be formed such that the longitudinal bore will belined with superhard material all along the length of the mixing tube,with the possible exception that, in the final AWJ mixing tube, theendmost part of the entryway length in some embodiments may not be linedwith a superhard material. In some of those embodiments in which theendmost part of the entryway length is not lined with a superhardmaterial, the present invention also includes coating the exposeddurable material in the endmost part of the entryway with a hard coatingdeposited by vapor deposition, i.e. by physical vapor deposition (PVD)and/or chemical vapor deposition (CVD). Examples of such hard coatingsinclude, without limitation, diamond, titanium nitride, titaniumcarbide, titanium carbonitride, titanium aluminum nitride, aluminumoxide, and their combinations.

[0018] The present invention also comprises AWJ mixing tubes comprisinga superhard material including those AWJ mixing tubes in which thesuperhard material is surrounded substantially along the length of themixing tube with a durable material which can act to reduce thesusceptibility of the mixing tube to damage from external forces, tofacilitate the adaptation of the superhard material into the AWJmachining head or to reinforce the superhard material so as to preventthe AWJ mixing tube from being damaged by water jet back pressure shouldthe mixing tube become plugged during operation. The present inventionalso includes AWJ mixing tubes comprising an entryway piece having asuperhard material formed on a tapered entryway bonded to an AWJ mixingtube body piece having a longitudinal bore lined with a superhardmaterial and methods of making such AWJ mixing tubes.

[0019] The present invention includes AWJ mixing tubes, and methods formaking same, comprising a flow passage formed by EDM in at least oneabrasion-resistant material piece, wherein at least part of the flowpassage has a lining comprising a superhard material. Included amongthese AWJ mixing tubes are single-component AWJ mixing tubes as well asmulti-component AWJ mixing tubes which comprise a plurality ofcomponents and at least one connection, which may be a disconnectableconnection, connecting one component to another such that the flowpassages of each of the individual components communicate with eachother to form the flow passage of the AWJ mixing tube and wherein theflow passage of least one of the plurality of components has a liningcomprising a superhard material. As already mentioned, as used herein,the term “component” refers to a discrete, hollow segment comprising aportion of the length of an AWJ mixing tube. Each component has a flowpassage which is part of the flow passage of the AWJ mixing tube. Thecomponents are connected end-to-end with each other to make the AWJmixing tube. For example, a two-component AWJ mixing tube according tothe present invention may have an entryway piece connected to an AWJmixing tube body piece wherein the entryway piece and the AWJ mixingtube body piece each has a flow passage formed in one or moreabrasion-resistant pieces and at least one of the entryway piece and theAWJ mixing tube body piece has part of its flow passage comprising asuperhard material. It is to be understood that, as used herein, an AWJmixing tube is considered to have a plurality of connected componentshaving at least one connection if, and only if, the AWJ mixing tubecomprising those components and connection or connections is an integralunit which can be handled and loaded into an AWJ cutting head as asingle piece.

[0020] The present invention also includes AWJ systems having a mixingtube comprising a superhard material. Such AWJ systems include AWJsystems having an AWJ mixing tube which includes a flow passage formedby EDM in at least one abrasion-resistant material wherein at least partof the flow passage has a lining comprising a superhard material. TheseAWJ systems include those AWJ systems having AWJ mixing tubes whichcomprise a plurality of components and at least one connection, whichmay be a disconnectable connection, connecting one component to anothersuch that the flow passages of each of the individual componentscommunicate with each other to form the flow passage of the AWJ mixingtube and wherein the flow passage or least one of the plurality ofcomponents has a lining comprising a superhard material. Such AWJsystems use any type of abrasive particles including, without limitationgarnet, olivine, alumina, cubic boron nitride, zirconia, siliconcarbide, boron carbide, diamond, other minerals and ceramics, and theirmixtures and combinations.

[0021] The present invention includes methods of using an AWJ systemcomprising the steps of providing an AWJ mixing tube having a flowpassage formed by EDM in at least one abrasion-resistant materialwherein at least part of the flow passage has a lining comprising asuperhard material, providing abrasive particles, emitting the abrasiveparticles from the AWJ mixing tube, and machining a workpiece with theemitted abrasive particles. Such a provided AWJ mixing tube may be onewhich comprises a plurality of components and at least one connection,which may be a disconnectable connection, connecting one component toanother such that the flow passages of each of the individual componentscommunicate with each other to form the flow passage of the AWJ mixingtube and wherein the flow passage of least one of the plurality ofcomponents has a lining comprising a superhard material. For examplewithout limitation, the present invention also includes methods of usingan AWJ system comprising the steps of providing an abrasive water jetmixing tube having a longitudinal bore lined with a superhard material,providing abrasive particles, emitting the abrasive particles from theabrasive water jet mixing tube, and machining a workpiece with theemitted abrasive particles.

[0022] Although AWJ systems typically use water as the carrier fluid,the present invention also contemplates the application of its methods,AWJ mixing tubes, and AWJ systems with the use of any fluid (gaseous orliquid) which is capable of acting as a fluid carrier in a system whichuses fluid-carried abrasive particles for cutting or machining aworkpiece. Such fluids include those which are capable of replacingwater, in whole or in part, as the carrier fluid in an AWJ system.Accordingly, the term “abrasive water jet” as used herein is not limitedto abrasive jets using water as the carrier fluid but instead refers toany abrasive jet having a fluid carrier.

[0023] The present invention also comprises a tubular elongate superhardmaterial body, and methods for making same, wherein the tubular elongatesuperhard material body has at least one bore formed by EDM which issubstantially parallel to the longitudinal axis of the tubular elongatesuperhard material body.

[0024] The present invention also comprises superhard material cylindershaving lengths of about 0.2 inches (5 mm) and diameters of about 0.2inches (5 mm) and either a straight or conical passage or a combinationof a straight and conical passage, along their longitudinal centerlines,formed by EDM machining. Such superhard material cylinders comprise asuperhard material or a composite of a superhard material bonded toanother abrasion-resistant material. Where a superhard material cylindercontains a straight passage, either alone or in conjunction with aconical passage, preferably the aspect ratio of the cylinder length tothe diameter of the passage is at least 4 to 1, and more preferably atleas: 6 to 1, and most preferably at least 10 to 1.

[0025] These and other features and advantages inherent in the subjectmatter claimed and disclosed will become apparent to those skilled inthe art from the following detailed description of presently preferredembodiments thereof and to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings are provided only as an aid in understanding theoperation of the present invention. It is to be understood, therefore,that the drawings are provided solely for the purpose of illustrationand not as a definition of the limits of the present invention.

[0027]FIG. 1 is a schematic drawing of a prior art computer-controlledAWJ system.

[0028]FIG. 2 is a longitudinal cross sectional view of a prior art AWJmachining head.

[0029]FIG. 3 is a longitudinal cross sectional view of an AWJ mixingtube comprised entirely of superhard material prepared according to afirst embodiment of the present invention.

[0030]FIG. 4 is a longitudinal cross sectional view of an AWJ mixingtube comprised of durable material with a superhard material coreprepared according to a second embodiment of the present invention.

[0031]FIG. 5 is an isometric view, shown partially in phantom, of amonolithic superhard material body.

[0032]FIG. 6 is a schematic drawing depicting some of the processingsteps of a second embodiment of the present invention.

[0033]FIG. 7 is a longitudinal cross sectional view of an AWJ mixingtube prepared according to a third embodiment of the present invention.

[0034]FIG. 8 is a schematic drawing depicting some of the processingsteps of a fourth embodiment of the present invention.

[0035]FIG. 9A is an isometric view of a composite disc comprisingsuperhard material formed in and bonded to grooves of a cementedtungsten carbide substrate.

[0036]FIG. 9B is a schematic drawing depicting some of the processingsteps of a fifth embodiment of the present invention.

[0037]FIG. 10 is a schematic drawing depicting some of the processingsteps of a sixth embodiment of the present invention.

[0038]FIG. 11A is a longitudinal cross sectional view of a portion of anAWJ mixing tube prepared according to a seventh embodiment of thepresent invention prior to the step of depositing a CVD diamond coating.

[0039]FIG. 11B is a longitudinal cross sectional view of a portion of anAWJ mixing tube prepared according to a seventh embodiment of thepresent invention after the step of depositing a CVD diamond coating.

[0040]FIG. 12 is a longitudinal cross sectional view of the entryway endportion of an AWJ mixing tube, prepared according to an eighthembodiment of the present invention, comprising an AWJ mixing tube bodyportion bonded to an entryway piece.

[0041]FIG. 13 is a longitudinal cross sectional view of an AWJ mixingtube prepared according to a ninth embodiment of the present invention.

[0042]FIG. 14 is a longitudinal cross sectional view of an AWJ mixingtube prepared according to a tenth embodiment of the present invention.

[0043]FIG. 15 is an isometric view of a tubular elongate superhardmaterial body according to an embodiment of the present invention.

[0044]FIG. 16A is an isometric longitudinal cross sectional view acrossthe midsection of a first embodiment of a superhard material cylinderaccording to the present invention.

[0045]FIG. 16B is an isometric longitudinal cross sectional view acrossthe midsection of a second embodiment of a superhard material cylinderaccording to the present invention.

[0046]FIG. 16C is an isometric longitudinal cross sectional view acrossthe midsection of a third embodiment of a superhard material cylinderaccording to the present invention.

[0047]FIG. 16D is an isometric longitudinal cross sectional view acrossthe midsection of a fourth embodiment of a superhard material cylinderaccording to the present invention.

DETAILED DESCRIPTION

[0048] To aid in the understanding of the present invention, adescription is first provided of a typical AWJ system and AWJ machininghead wherein water is the carrier fluid before embodiments of thepresent invention are described.

[0049]FIGS. 1 and 2, respectively show a schematic of a typicalcomputer-guided AWJ system and a cross-section of a typical AWJmachining head. Referring to FIGS. 1 and 2, in computer-guided AWJsystem 1, water 2 is forced by a booster pump 4 at about 65 to 85 psi(450 to 590 kPa) through a filter 6 and then into an intensifier pump 8where it is pressured to the range of 2,000 to 100,000 psi (14 to 690MPa). The high pressure water 2 is delivered through swivelled highpressure piping 10 to an AWJ machining head 12 which is controlled bycomputer 13 and AWJ head moving mechanism 17 to be indexed along thethree mutually-orthogonal axises X, Y, and Z. The high pressure water 2enters into the high pressure water reservoir 11 of the AWJ machininghead 12 and is forced out through a nozzle 16 to form a high-velocityjet 24. The high-velocity jet 24 passes through mixing chamber area 18into which abrasive particles 15 are fed from an outside source 14. Thehigh-velocity jet 24 and the abrasive particles 15 together flow throughthe longitudinal bore 20 of the AWJ mixing tube 22 and exit as abrasivewater jet 25. The abrasive water jet 25 is directed against workpiece 26machining workpiece 26 before being dissipated and collected incollection tank 27. AWJ mixing tube 22 has an overall length 28.

[0050] Embodiments of the present invention will now be discussed. Theembodiments are discussed in some cases with reference to AWJ systemswhich employ water as the carrier fluid. However, it is to be understoodthat the reference to water is made for convenience and is in no waymeant to limit the present invention to use with AWJ systems employingwater as the carrier fluid. FIG. 3 shows a longitudinal cross sectionalview of a first AJW mixing tube prepared according to the presentinvention in which the mixing tube consists solely of superhardmaterial. Referring to FIG. 3, first AWJ mixing tube 30 has an entry end31, entry end face 32, a tapered entryway 34, a longitudinal bore 36, anexit end 38, and an exit end face 39. In operation, the high velocitywater jet and the stream of abrasive particles enter AWJ mixing tube 30through entryway 34 and pass through longitudinal bore 36 before exitingAWJ mixing tube 30 at exit end 38 as an abrasive water jet. AWJ mixingtube 30 also has external taper 40 abutting exit end face 38. Externaltaper 40 facilitates bringing AWJ mixing tube 30 in close proximity withsome workpieces.

[0051]FIG. 4 shows a longitudinal cross sectional view of a second AJWmixing tube prepared according to the present invention in which secondAWJ mixing tube 42 has superhard material core 44 lining AWJ mixing tubelongitudinal bore 36 and durable material 45 surrounding the superhardmaterial core 44 substantially along the length 46 of AWJ mixing tube42. A portion of superhard material core 44 was machined away during theformation of tapered entryway 34 so that durable material 45 extendsbeyond superhard material core 44 at entry end 31.

[0052] The methods of the present invention may be used to produce alltypes of AWJ mixing tubes for use in current and future AWJ machininghead designs. Those designs therefore determine the dimensions of theAWJ mixing tubes produced according to the present invention. Ingeneral, in AWJ systems in which water is the carrier fluid, current AWJmixing tubes are cylindrical with overall lengths on the order of 2 to 4inches (5 to 10 cm), outside diameters on the order of 0.2 to 0.4 inches(5 to 10 mm), and longitudinal bore diameters on the order of 0.010 toabout 0.060 inches (0.25 to 1.5 mm). AWJ mixing tube longitudinal boresusually have circular cross-sections, although non-circular crosssections and non-straight-walled longitudinal bores are also known inthe art and are within the scope of the present invention. Examples ofAWJ mixing tubes with longitudinal bores having noncircular crosssections are described for by Rankin et al., U.S. Pat. No. 5,626,508,which is incorporated herein by reference.

[0053] The use of EDM to form PCD and EDM-machinable PCBN is well knownin the art. Therefore, the conditions necessary for each of the EDMoperations utilized in the performance of the present invention may bereadily ascertained by one skilled in the art without resort to undueexperimentation. One skilled in the art will recognize that the specificEDM parameters will vary according to the particular workpiece beingmachined and the particular EDM operation being employed.

[0054] An AWJ mixing tube consisting solely of a superhard material maybe made according to a first embodiment of the present invention by thefollowing method. Referring to FIG. 5, first, a monolithic superhardmaterial body 50 having a length 52, width 54, and thickness 56, eachbeing sufficient to yield the final AWJ mixing tube dimensions, isprovided. Length 52 is at least about 1 inch (2.5 cm) in order to make a1 inch (2.5 cm) long AWJ mixing tube. Length 52 is preferably in therange of from about 1 to about 4 inches (2.5 to 10 cm) and morepreferably in the range of from about 1.5 to about 3 inches (3.8 to 7.6cm). The external dimensions of superhard material body 50 are alteredas necessary at this time or later by EDM or other techniques known tothose skilled in the art e.g., laser cutting, diamond saw or wirecutting, grinding etc., to produce the final AWJ mixing tube dimensions.Preferably, first and second end faces 58, 59 are made mutually paralleland perpendicular to the longitudinal axis of superhard material body50. First and second end faces 58, 59 shown in FIG. 5 correspondrespectively to AWJ mixing tube entry end face 31 and AWJ mixing tubeexit end face 39 of FIG. 3. EDM plunge forming is then used to form atapered entryway, such as tapered entryway 34 shown in FIG. 3, in firstend face 58. EDM drilling is then used to form a longitudinal bore, suchas longitudinal bore 36 shown in FIG. 3, along the longitudinal axis ofthe superhard material body 50 from the apex of the tapered entrywaythrough second end face 59.

[0055] A method according to a second embodiment of the presentinvention will now be described for producing an AWJ mixing tube havinga superhard material-lined longitudinal bore surrounded by a durablematerial. Referring to FIG. 6, a monolithic superhard material body 60is provided. Superhard material body 60 has a width 62 and thickness 64sufficient to provide at least 0.005 inches (0.13 mm), and morepreferably at least 0.010 inches (0.25 mm), of superhard materialthickness surrounding the AWJ mixing tube longitudinal bore in theresulting AJW mixing tube. Superhard material body 60 also has a length66 sufficient to yield the final AWJ mixing tube length. First andsecond durable material bodies 68, 70 are also provided, having lengths72, 74 respectively which are sufficient to yield the final AWJ mixingtube length. First durable material body 68 has diameter 76 sufficientto yield the outside dimensions of the resulting AWJ mixing tube. Firstdurable material body 68 has a cavity 78 adapted to coextensivelyreceive both body 60 and second durable body 70 along with bondingmaterial 80. First durable material body 68, superhard material body 60,and bonding material 80 are assembled together into assembly 82 suchthat superhard material body 60 forms a core section along thelongitudinal centerline of assembly 82 with second durable material body70 and bonding material 80 substantially filling the remaining portionof cavity 78. Preferably, superhard material body 60 and second durablematerial body 70 fit in cavity 78 with just enough clearance toaccommodate bonding material 80. A sufficient amount of bonding material80 is used to bond together assembly 82 with sufficient strength anduniformity as is required for the later manufacturing steps andin-service use of the resulting AWJ mixing tube. The assembly 82 isbonded together using whatever fixturing may be appropriate under thecircumstances, to form AWJ mixing tube blank 84. Where bonding material80 is a brazing material, the bonding step is accomplished by raisingthe temperature of assembly 82 to the appropriate brazing temperatureand then cooling assembly 82 at a cooling rate that will safeguard thephysical integrity of AWJ mixing tube blank 84. Where bonding material80 is an adhesive, the steps necessary for curing the adhesive areperformed. After the bonding has been completed, the external dimensionsof AWJ milling tube blank 84 are altered as necessary at this time orlater by the machining techniques known to those skilled in the artwhich are appropriate for the durable material to produce the final AWJmixing tube-dimensions. Preferably, first and second end faces 86, 88 ofthe AWJ milling tube blank 84 are made mutually parallel andperpendicular to the longitudinal axis of the AJW mixing tube blank 84.A tapered entryway, such as tapered entryway 34 as shown in FIG. 4, isthen formed in first end face 86, preferably by EDM plunge forming. EDMdrilling is then used to form the AWJ mixing tube longitudinal bore,such as longitudinal bore 36 as shown in FIG. 4, along the longitudinalaxis of the AWJ milling tube blank 84 from the apex of the taperedentryway through second end face 88. Final machining of AWJ milling tubeblank 84 may then be performed as necessary to yield the final outerdimensions of the AWJ mixing tube.

[0056] In a third embodiment of the present invention, a plurality ofindividual superhard material bodies are provided in the above methodinstead of a single superhard material body. In this embodiment, each ofthe individual superhard material bodies has a first and second end facesuch that the distance between the first and second end face comprisesthe length of the individual superhard material body. The embodimentincludes abutting at least one of the first and second end faces of eachindividual superhard material body against one of the first and secondend faces of another individual superhard material body so that theplurality of the individual superhard material bodies together form thesuperhard material core of the AWJ mixing tube blank. In other words,the individual superhard material bodies are placed end to end to yieldthe overall length of the AWJ mixing tube superhard material core.

[0057]FIG. 7 shows a cross sectional view of AWJ mixing tube 90 made inaccordance with this third embodiment of the present invention. AWJmixing tube 90 includes a plurality of individual superhard materialbodies, first, second, and third superhard material bodies 92, 94, 96which together comprise segmented superhard material core 97. In thecondition in which the individual superhard material bodies wereprovided prior to assembly, each of the individual superhard materialbodies 92, 94, 96 had a first and second end face such that the distancebetween the first and second end faces comprised the length of theindividual superhard material body. For example, second superhardmaterial body 94 had and still has end faces 98, 100, with the distancebetween them comprising the length 102 of second superhard material body94. However, during the formation of the tapered entryway 34, a portionof first superhard material body 92 was machined away, which includedwhat was its first face in the as-provided condition. End face 104 offirst superhard material body 92 abuts end face 98 of second superhardmaterial body 94 along first interface 106 and end face 100 of secondsuperhard material body 94 abuts end face 108 of third superhardmaterial body 96 along second interface 110. It is important that theend faces of adjacent superhard material bodies are abutted togetherprecisely enough to avoid excessive erosion wear at the abutmentinterfaces during the operation of the resulting AWJ mixing tube. Forexample, end faces 100, 108 of adjacent superhard material bodies 94, 96are abutted together precisely enough to avoid excessive erosion wear atabutment interface 110 in third AWJ mixing tube 90. Excessive erosion islocalized erosion that is substantially greater than that erosionoccurring generally along the AWJ mixing tube longitudinal bore. Thus,it is preferred that each of the end faces of the individual superhardmaterial bodies be machined and/or ground flat, co-parallel with itsopposing face, and perpendicular to the superhard material body'slongitudinal axis.

[0058] Referring to FIG. 8, in a fourth embodiment of the presentinvention, wherein cemented carbide is used as the durable material,superhard material is provided as part of composite 112. Composite 112has a superhard material layer 114 bonded to a cemented tungsten carbidesubstrate 116. Preferably, superhard material layer 114 is formed oncemented tungsten carbide substrate 116 during the superhard materialsynthesis process and composite 112 is a strip that has been EDMmachined from a disc of a superhard material-cemented tungsten carbidecomposite that resulted from the superhard material synthesis process.Composite 112 is coextensively received into cavity 118 of durablematerial body 120 along with bonding material 122 so that superhardmaterial layer 114 forms a core section along the longitudinalcenterline of assembly 124 and cemented carbide substrate 116 ofcomposite 112 fills at least some, and preferably all, of the remainingportion of cavity 118 with just enough clearance to accommodate bondingmaterial 122. Where the composite along with bonding material does notcompletely fill the receiving cavity, then one or more supplementaldurable material bodies are provided and used to substantially fill theremaining space in the cavity. Assembly 124 is then bonded to form AWJmixing tube blank 126 which is then processed utilizing the steps asdescribed above for other embodiments of the present invention.

[0059] So far for embodiments of the present invention in which adurable material is used, the durable material is described as beingsupplied in the form of a cylindrical body with a cavity for receiving asuperhard material body and additional durable material to complete thelongitudinal surrounding of the superhard material body with durablematerial. However, the present invention also includes methods forassembling any configurations of durable material and superhard materialbodies that can be bonded together to form an AWJ mixing tube blankhaving a core of superhard material surrounded substantially along thelength of the AWJ mixing tube blank by durable material. The onlyrestrictions contemplated by the present invention for such methods arethat (1) the AWL longitudinal bore be surrounded by superhard materialof at least 0.005 inches (0.13 mm), and preferably, at least 0.010inches (0.25 mm) thick, and (2) where a plurality of superhard materialbodies are used to form the superhard material core, that the faces ofadjacent superhard material are made to abutt together precisely enoughto avoid excessive erosion wear at the abutment interfaces during theoperation of the resulting AWJ mixing tube.

[0060] For example, in a fifth embodiment of the present invention, amajor portion of the durable material is not provided as in the form ofa cylindrical body having a cavity for receiving a body superhardmaterial body but rather is provided as part of a composite of thedurable material and superhard material. Referring to FIG. 9A, superhardmaterial body 128 is formed in and is bonded to a groove 130 of acemented tungsten substrate 132 of composite disc 134. Composite disc134 is sectioned, preferably by EDM machining, into strips such ascomposite strip 136, with each strip having a superhard material body128 surrounded on three sides by cemented tungsten carbide as durablematerial 138. A durable material closure body 140 of a cemented tungstencarbide is provided and placed onto face 142 of composite strip 136along with bonding material 144 to form assembly 146. Durable materialclosure body 140 is then bonded to composite strip 136 to form AWJmixing tube blank 148 which is then processed into an AWJ mixing tubeutilizing the steps described above for other embodiments of the presentinvention.

[0061] As a further example of possible configurations of durablematerial and superhard material bodies that can be used according to thepresent invention, in a sixth embodiment, referring to FIG. 10, u-shapeddurable material body 150 having cavity 152 is provided. A superhardmaterial body 154 is provided as part of composite body 156. Compositebody 156 comprises superhard material body 154 formed on and bonded tocemented tungsten carbide substrate 158. Composite body 156 iscoextensively received into cavity 152 of u-shaped durable material body150 along with bonding material 160 so that superhard material body 154forms a core section along the longitudinal centerline of assembly 162and cemented tungsten carbide substrate 158 of composite body 140 fillsat least some, and preferably all, of the remaining portion of cavity152 with just enough clearance to accommodate bonding material 160.Assembly 162 is then bonded to form AWJ mixing tube blank 164 which isthen processed utilizing the steps as described above for otherembodiments of the present invention.

[0062] In some of embodiments of the present invention in which atapered entryway is formed in the AWJ mixing tube in a manner whichcauses a portion of the durable material to be exposed in the entryway,the present invention optionally includes the step of depositing a hardcoating by vapor deposition, i.e. by physical vapor deposition (PVD)and/or chemical vapor deposition (CVD), on the exposed durable material.Examples of such hard coatings include, without limitation, diamond,titanium nitride, titanium carbide, titanium carbonitride, titaniumaluminum nitride, aluminum oxide, and their combinations. The hardcoating provides protection to the underlying durable material thatwould otherwise be exposed to erosion by the high velocity water jet andthe abrasive particles entering the AWJ mixing tube entryway. The hardcoating may consist of one or more layers and may be applied eitherdirectly onto the exposed durable material or onto one or moreintermediate layers of other materials deposited to promote the adhesionor durability of the hard coating. The thickness of the hard coating ispreferably in the range of 1 to 50 micrometers.

[0063] For example, FIGS. 11A and 11B show respectively the entryportion of an AWJ mixing tube prepared by a method according to aseventh embodiment of the present invention before and after a CVDdiamond coating has been directly deposited onto exposed durablematerial in the entryway. Referring to FIG. 11A, in this embodiment, theAWJ mixing tube 166 is prepared utilizing the steps described above forother embodiments of the present invention in which an entryway isformed. In this case, the formation of entryway 34 has removed a portionof superhard material core 44 nearest entry end 31 of AWJ mixing tube166 causing durable material 45 to have exposed face 168 inside ofentryway 34 adjacent to superhard material core face 170. Referring toFIG. 11B, after entryway 34 has been formed, a diamond coating 172 isapplied by CVD in one or more layers on the durable material exposedface 168 in the entryway 34. Preferably, diamond coating 172 alsoextends over at least a portion of superhard material core face 170 sothat the junction 174 between the durable material exposed face 168 andsuperhard material core face 170 is covered by the CVD diamond coating172. Techniques for depositing hard coatings by CVD are well known inthe art and the conditions necessary for depositing a CVD hard coatingin this step may be readily ascertained by one skilled in the artwithout resort to undue experimentation.

[0064] Embodiments of the present invention include AWJ mixing tubes,and methods for making same, comprising a flow passage formed by EDM inat least one abrasion-resistant material piece, wherein at least part ofthe flow passage has a lining comprising a superhard material. Thethickness of the superhard material lining is preferably at least about0.005 inches (0.13 mm) and more preferably at least about 0.010 inches(0.25 mm). Included among these embodiments are single-component AWJmixing tubes as well as multi-component AWJ mixing tubes which comprisea plurality of components and at least one connection, which may be adisconnectable connection, connecting one component to another such thatthe flow passages of each of the individual components communicate witheach other to form the flow passage of the AWJ mixing tube and whereinthe flow passage of at least one of the plurality of components has alining comprising a superhard material. For example, the presentinvention includes AWJ mixing tubes comprising an entryway piececonnected to an AWJ mixing tube body piece. The present invention alsoincludes AWJ mixing tubes having a connected exit section. It is to beunderstood that, as used herein, an AWJ mixing tube is considered tohave a plurality of connected components having at least one connectionif, and only if, the AWJ mixing tube comprising those components andconnection or connections is an integral unit which can be handled andloaded into an AWJ cutting head as a single piece.

[0065] In embodiments which include a disconnectable connection,preferably at least one of the AWJ mixing tube component parts which isconnected by the disconnectable connection is potentially reusable. Ascontemplated by the present invention, a connection is disconnectable solong as the procedure by which the connection was made can be reversedto disconnect the components without damaging the reusable component tothe point where it is unsuitable for further use. For example withoutlimitation, a disconnectable connection may be made by threading, pressfitting, brazing or adhesively bonding together the mating ends ofadjacent components.

[0066] In embodiments of the present invention which comprise one ormore connections between component parts of an AWJ mixing tube, eachconnection is formed so that the flow passage of the AWJ mixing tube iscontinuous and unobstructed and adjacent components are abutted togetherprecisely enough to avoid excessive erosion wear at their interfacesduring the operation of the AWJ mixing tube.

[0067] The present invention also includes embodiments in which an AWJmixing tube having superhard material-lined longitudinal bore includesan AWJ mixing tube body portion bonded to an entryway piece. Theentryway piece in these embodiments has a tapered entryway that isformed in a durable material substrate and superhard material which isformed on the tapered entryway of the durable material substrate.Preferably, but not necessarily, the entryway piece also has a boresection extending from the apex of its tapered entryway and superhardmaterial is also formed on this bore section. The thickness of thesuperhard material on the tapered entryway and on the optional boresection of the entryway piece is at least about 0.005 inches (0.13 mm)and more preferably at least about 0.010 inches (0.25 mm). The superhardmaterial thickness of the entryway piece may be the same or differentfrom the thickness of the superhard material of the AWJ mixing tube bodyportion. The AWJ mixing tube body portion is produced utilizing thesteps described above for other embodiments of the present invention formaking an AWJ mixing tube having a superhard material-lined longitudinalbore with the exception of forming the entryway portion. The entrywaypiece and the body portion are bonded together such that the centerlineof the tapered entryway of the entryway piece and the centerline of thebore of the AWJ mixing tube body portion are essentially collinear. Thebonding may be accomplished by using a bonding material such as a brazeor an adhesive.

[0068]FIG. 12 shows the entryway end of an AWJ mixing tube according toan eighth embodiment of the present invention wherein the AWJ mixingtube comprises an entryway piece and an AWJ mixing tube body portion.Referring to FIG. 12, AWJ mixing tube 176 includes entryway piece 178and AWJ mixing tube body piece 180 which are bonded together. Entrywaypiece 178 consists of durable material substrate 182 having taperedentryway 184 and bore extension 186 onto which superhard material 188was formed. AWJ mixing tube body piece 180 includes durable material 45,superhard material core 44 and longitudinal bore 36. Superhard materialend face 190 of entryway piece 178 and core end face 192 of AWJ mixingtube body piece 180 abut each other along interface 194. It is importantthat end faces 190, 192 are abutted together precisely enough to avoidexcessive erosion wear at interface 194 during the operation of theresulting AWJ mixing tube.

[0069]FIG. 13 shows an AWJ mixing tube according to a ninth embodimentof the present invention. This embodiment illustrates the use of athreaded joint to disconnectably connect the components of an AWJ mixingtube according to the present invention. This embodiment alsoillustrates additional construction configurations which can be used forconstructing AWJ mixing tubes in accordance with the present invention.

[0070] In this embodiment, AWJ mixing tube 200 comprises top section 202which is disconnectably connected to bottom section 204 at threadedjoint 206. Top section 202 consists of cylindrical composite disk 208and one or more superhard material disks, e.g., cylindrical superhardmaterial disks 210-224. These disks are enclosed within upper sectionjacket 226. Composite disk 208 and superhard material disk 210 extendradially to upper jacket section 226. Superhard material disks 210-224need not extend that far radially and may have some otherabrasion-resistant material interposed between their outer periphery andupper jacket section 226.

[0071] Each of the superhard material disks 210-224 may be cut from alarger piece of superhard material by EDM or other means known to oneskilled in the art or may be synthesized to, or near to, their finaldimensions. The thickness in the longitudinal direction need not be thesame for all of the superhard material disks 210-224 and may take on anyvalue, but each superhard material disk 210-224 preferably has athickness in the range of about 0.06 to about 0.2 inches (1.5 to 5 mm).

[0072] Composite disk 208 comprises tungsten carbide layer 228 andsuperhard material layer 230 which are bonded together-the bondingpreferably occurring during the formation process of superhard materiallayer 230. Tungsten carbide layer 228 forms rim 231 on entry end 236 ofAWJ mixing tube 200. Although a superhard material disk could be used inplace of composite disk 208, it is more preferable that the disk atentry end 236 of the AWJ mixing tube 200 be made of a composite materialconsisting of a superhard material and an abrasion-resistant materialwhich is less hard than a superhard material. This is because it iseasier to form a recess, such as recess 232, to receive upper sectionjacket shoulder 234 in rim 231 in such an abrasion-resistant materialthan it is in a superhard material. The thickness of the abrasionresistant material should be as small as possible while still allowingformation of the recess.

[0073] The transition between the tapered entryway and the bore sectionis preferably located away from an interface between a composite diskand a superhard material disk or an interface between two superhardmaterial disks. FIG. 13 illustrates this preference as transition 235between tapered entryway 237 and upper longitudinal bore 238 is locatedwithin a superhard material disk, superhard material disk 210, and awayfrom such interfaces.

[0074] Top section 202 may be constructed by assembling composite disk208 and superhard material disks 210-224 into upper section jacket 226and then EDM machining of the tapered entryway 237 and upper sectionlongitudinal bore 238 may be done. EDM machining these portions of flowpassage 240 of AWJ mixing tube 200 after the disks 208-224 have beenassembled together avoids mismatches at the junctions of adjacent disksalong flow passage 240 thereby minimizing erosion at those locationsduring the operation of AWJ mixing tube 200. Preferably, the adjacentfaces of adjacent disks are prepared to enhance their mating with oneanother. This may be done, for example without limitation, by EDMplaning and/or mechanically grinding or polishing adjacent faces tomatch each other's contours. It is important that the end faces ofadjacent superhard material disks are abutted together precisely enoughto avoid excessive erosion wear at the abutment interfaces during theoperation of the resulting AWJ mixing tube.

[0075] The step of assembling the superhard material disks together maybe accomplished in a variety of ways. For instance, as is the case inFIG. 13, the disks 208-224 may be simply inserted or pressed against oneanother into upper body jacket 226. Alternatively, adjacent disks may bebonded together by adhesives or by brazing prior to or after they havebeen inserted into the jacket. Small amounts of a gasketing material orvery thin shims may be used between the faces of adjacent superhardmaterial disks to improve their mating or to protect the superhardmaterial disks from damage during the insertion or press fittingoperations. Preferably, a spacing material is used to fill in any spacebetween the assembled superhard material disks and the jacket to fix thelocation of the superhard material disks in relation to the jacket.

[0076] Referring still to FIG. 13, bottom section 204 comprisesabrasion-resistant material core 242, first and second centeringcouplings 244, 246, spacing material 248, and bottom section jacket 250.The abrasion-resistant material comprising abrasion-resistant materialcore 242 is most preferably a superhard material. A “centeringcoupling,” as that term is used herein, is a device which serves tocenter one or more pieces of abrasion-resistant material within an AWJmixing tube jacket so that the abrasion-resistant material piece orpieces are positioned to properly align the AWJ mixing tube bore. Acentering coupling also serves to hold the abrasion-resistant materialcentered in place while a spacing material is inserted between theabrasion-resistant material and the jacket. In embodiments employingcentering couplings, one or more centering couplings may be used.Preferably, a center coupling is tubular in shape and has an outsidediameter which makes a close sliding fit with the inside diameter of thejacket into which it is to be inserted and an inside diameter that makesa close sliding fit with the abrasion-resistant material piece or piecesthat it will contain. Where a single centering coupling is used with twoabrasion-resistant material pieces and the cross-sectional size and/orshape of one of the abrasion-resistant material pieces differs from thatof the other, the interior of the centering coupling should be adaptedto closely receive each of the abrasion-resistant material pieces. Anygaps that exist between the centering coupling interior and theabrasion-resistant material piece or pieces may be filled in with aspacing material.

[0077] Bottom section 204 may be constructed by first sliding first andsecond centering couplings 244, 246 onto the opposite ends ofabrasion-resistant material core 242. This assembly is inserted intobottom section jacket 250. Space filling material 248 is then interposedbetween bottom section jacket 250 and abrasion-resistant material core242 by injecting space filling material 248 in fluid form throughinjection port 252. Spacing material 248 also flows into any gaps thatmight exist between abrasion-resistant material core 242 and first andsecond centering couplings 244, 246. Bottom section longitudinal bore254 may be EDM machined into abrasion-resistant material core 242 atthis time.

[0078] Top and bottom sections 202, 204 are connected together bythreadably connecting these two components together at joint 206 untilthe upper end face 256 of abrasion-resistant material core 242 comesinto mating contact with lower end face 258 of lowermost superhardmaterial disk 224. Preferably, end faces 256, 258 are conditioned sothat they abut one another precisely enough to avoid excessive erosionwear at their interface during the operation of AWJ mixing tube 200.Gasket 260 is optionally used at the junction of top and bottom sections202, 204 to help avoid the over tightening of these two components so asto prevent damaging abrasion-resistant core 242 or lower-most superhardmaterial disk 244.

[0079] As was just described, the separate portions of flow passage 240which are located, respectively, in the top and bottom sections 202, 204may be machined prior the joining together of these components of AWJmixing tube 200. Another option is to wait until after the top andbottom sections are joined together to do some or all of the EDMmachining of flow passage 240. The former approach has the advantage offacilitating the replacement of a worn component during the use of theAWJ mixing tube, while the latter approach has the advantage of reducingthe chance of mismatch at the junction of the lower-most superhardmaterial disk 224 and abrasion-resistant material core 242 andminimizing erosion at their interface.

[0080] Although top and bottom sections 202, 204 components of AWJmixing tube 200 are shown as having different constructions, it is to beunderstood that these components may have similar constructions.Furthermore, the construction of either component may be made accordingto any manner or combination of manners which have been described withregard to any of the embodiments of the present invention. It is also tobe understood that embodiments of the present invention which comprisecomponents which are disconnectably connected together may include anynumber of components and that the relative lengths of the components maytake on any value.

[0081]FIG. 14 illustrates a tenth embodiment of an AWJ mixing tubeaccording to the present invention. This embodiment illustrates the useof an abrasive resistant material other than a superhard material liningthe bore in an intermediate region of the flow passage of the AWJ mixingtube. Referring to FIG. 14, AWJ mixing tube 300 comprises top section302 which is disconnectably connected to bottom section 304 at threadedjoint 306. Comparing to FIGS. 13 and 14, it can be seen that AWJ mixingtube 300 is the same as AWJ mixing tube 200, except that superhardmaterial disks 216-224 of AWJ mixing tube 200 have been replaced withabrasion-resistant material cylinder 308 which is a non-superhardmaterial. Although, the present invention contemplates that any portionof AWJ mixing tube flow passage can be lined with an abrasion-resistantmaterial that is not a superhard material so long as at least theportion of the flow passage that is of particular concern to the user islined with a superhard material, in terms of maximizing the working lifeof the AWJ mixing tube, it is preferred that the use ofabrasion-resistant materials which are not superhard materials beconfined to the flow passage region wherein the abrasive particles flowin a columnated stream, since such a region is less subject to abrasivewear during the operation of the AWJ mixing tube than are regions inwhich the particle flow is not in a columnated stream.

[0082] The present invention also includes among its embodiments all AWJmixing tubes having superhard material lining the longitudinal bore ofthe AWJ mixing tube. Preferably, at least 0.005 inches (0.13 mm), andmore preferably at least 0.010 inches (0.25 mm), of superhard materiallining thickness surrounds the AWJ mixing tube longitudinal bore inthese embodiments.

[0083] The present invention also includes among its embodiments AWJsystems having a mixing tube comprising a superhard material. Suchembodiments include AWJ systems having an AWJ mixing tube which includesa flow passage formed by EDM in at least one abrasion-resistant materialwherein at least part of the flow passage has a lining comprising asuperhard material. These AWJ systems include those AWJ systems havingAWJ mixing tubes which comprise a plurality of components and at leastone connection, which may be a disconnectable connection, connecting onecomponent to another such that the flow passages of each of theindividual components communicate with each other to form the flowpassage of the AWJ mixing tube and wherein the flow passage of at leastone of the plurality of components has a lining comprising a superhardmaterial. Such AWJ systems may include a booster pump, filter,intensifier pump, high pressure pumping, AWJ machining head, AWJmachining head moving mechanism, and collection tank such as thosedepicted in the prior art system illustrated in FIG. 1.

[0084] AWJ systems of the present invention having a mixing tubecomprising a superhard material use any type of abrasive particlesincluding, without limitation garnet, olivine, alumina, cubic boronnitride, zirconia, silicon carbide, boron carbide, diamond, and otherminerals and ceramics and their mixtures and combinations. Preferably,such AWJ systems use abrasive particles having a hardness greater thangarnet, for example, alumina, cubic boron nitride, diamond or theircombinations with each other and other materials and their mixtures andcombinations. Where abrasive particles such as diamond are used, thediamond particles may be recovered from the collection tank, cleaned andre-used where cost effective.

[0085] The present invention includes methods of using an AWJ systemcomprising the steps of (1) providing an AWJ mixing tube having a flowpassage formed by EDM in at least one abrasion-resistant materialwherein at least part of the flow passage has a lining comprising asuperhard material; (2) providing abrasive particles; (3) emitting theabrasive particles from the AWJ mixing tube; and (3) machining aworkpiece with the emitted abrasive particles. Such a provided AWJmixing tube may comprise a plurality of components and at least oneconnection, which may be a disconnectable connection, connecting onecomponent to another such that the flow passages of each of theindividual components communicate with each other to form the flowpassage of the AWJ mixing tube and wherein the flow passage of least oneof the plurality of components has a lining comprising a superhardmaterial. For example without limitation, the present invention alsoincludes among its embodiments methods of using an AWJ system comprisingthe steps of providing an abrasive water jet mixing tube having alongitudinal bore lined with a superhard material, providing abrasiveparticles, emitting the abrasive particles from the abrasive water jetmixing tube, and machining a workpiece with the emitted abrasiveparticles. Such methods may include the step of selecting the abrasiveparticles from the group consisting of cubic boron nitride, diamond,their combinations with each other and other materials. Where abrasiveparticles are so selected from this group, the methods of the presentinvention include machining any type of workpiece, including workpiecescomprising, in whole or in part, a material having a hardness of about 9or greater on the Mohs scale. Note that all references herein to theMohs scale are to the original Mohs hardness scale on which diamond hasa Mohs hardness of 10. Examples of materials having a hardness of about9 or greater include, without limitation diamond and cubic boronnitride.

[0086] The present invention contemplates that the durable material beany material that is capable of being bonded to superhard material or ofacting to reduce the susceptibility of the AWJ mixing tube to damagefrom external forces or to facilitate the adaption of the superhardmaterial core lining into the AWJ machining head. Preferably, thedurable material also is capable of reinforcing the superhard materialso as to prevent the AWJ mixing tube from being damaged by water jetback pressure should the AWJ mixing tube become plugged duringoperation. Examples of such materials, include without limitation,steels, cemented tungsten carbides, ceramics and cermets. However, inAWJ mixing tube designs in which the durable material is exposed toerosive wear from the high velocity water jet and abrasive particlesduring the AWJ operation, such as in designs in which a portion of thedurable material is exposed as part of the tapered entryway of the AWJmixing tube, the durable material is preferably a steel or a cementedtungsten carbide. Preferred steels include abrasive resistant alloy ortool steels such as steel grades 4140, 4340, H13, and A8. Preferredcemented tungsten carbide grades include those grades which containapproximately 0 to 20 weight percent binder (e.g. cobalt orcobalt-nickel alloys), more preferably approximately 6 to 16 weightpercent binder.

[0087] The present invention contemplates that the bonding material beany bonding material that is capable of bonding superhard material tothe particular type durable material that is being utilized during thepractice of the invention. Although for convenience sake in theaccompanying drawings, the bonding material has been represented in theform of thin strips, the present invention also contemplates usingbonding material in any form that facilitates the bonding of thesuperhard material and the durable material bodies. Furthermore,although the methods described herein have described the bondingmaterial as being assembled with the durable material and superhardmaterial bodies into an assembly, the present invention alsocontemplates the addition of bonding material by any means that resultsin the durable material and superhard material bodies being bondedtogether into an AWJ mixing tube blank. For example, the presentinvention includes assembling the durable material and superhardmaterial bodies into an assembly and then infiltrating the assembly witha fluid bonding material. Examples of suitable bonding materials includebrazes and adhesives. When a cemented tungsten carbide is used as thedurable material, the bonding material is preferably a brazing alloy. Anexample of a suitable brazing alloy is a brazing alloy having a liquidusof 606 C and containing 15% copper, 16% zinc, 45% silver, and 24%cadmium such as Easy-Flo 45 which is available from Handy & Harman ofCanada, Limited, 290 Carlingview Drive, Rexdale, Ontario, Canada M9W5G1.When a steel is used as the durable material, the bonding material ispreferably an adhesive. An example of suitable adhesive is a two-part,room temperature curable organic adhesive such as Aremco-Bond(TM) 631which is available from Aremco Products, Inc. P.O. Box 429, Ossining,N.Y., 10562.

[0088] Commercially available PCD is suitable for use with the presentinvention. PCD is commercially available in the form of sheets and disksin thicknesses up to about 0.2 inches (5 mm). Disks of PCD arecommercially available in diameters up to about 3 inches (78 mm). PCD iscommercially available in a variety of grain sizes and with metalliccontents of about 4 to 8 volume percent. This metallic content mayinclude, for example, without limitation, cobalt or cobalt-nickelalloys. The average PCD grain size may be on the order of 0.1 to 100micrometers. Examples of currently commercially available PCD gradeshave nominal average grain sizes of about 2, 10, 25, and 75 micrometers.PCD that is suitable for with the present invention is available fromDiamond Abrasives Corp, 35 West 45th Street, New York, N.Y. 10036, andfrom General Electric, 6325 Huntley Road, Box 568, Worthington, Mass.43085.

[0089] The present invention contemplates abrasion-resistant material toinclude superhard materials, as defined herein, as well as lower costmaterials known to one skilled in the art that are capable ofsubstantially resisting abrasion by the abrasive particles that are tobe used in conjunction with the AWJ mixing tube. For example withoutlimitation, such lower cost abrasion-resistant materials includecemented tungsten carbide or tool steel. Preferred cemented tungstencarbide grades include those grades which contain approximately 0 to 10weight percent binder (e.g. cobalt or cobalt-nickel alloys), morepreferably approximately 0 to 3 weight percent binder. For example,ROCTEC 100 and ROCTEC 500 are available from Kennametal Inc., ofLatrobe, Pa. 15650. Preferred steels include abrasion resistant alloy ortool steels such as steel grades 4140, 4340, H13, and A8.

[0090] The present invention contemplates that materials that aresuitable for the jackets include steel, aluminum, plastics and othermaterials known to one skilled in the art that are adaptable for such ause. Preferably, the jacket material will be a strong, resilientmaterial.

[0091] The present invention contemplates that materials which aresuitable for the centering couplings include metals and plastics or anyother suitable materials which are known to one skilled in the art asbeing adaptable for such a use. Preferably, the material will be aresilient material and is most preferably a low carbon steel.

[0092] The present invention contemplates that the spacing material maybe a material such as a metal, a plastic, or a potting compound or anyother materials known to one skilled in the art that is capable offixing the superhard material or other abrasion-resistant pieces whichcomprise the entryway and core of the AWJ mixing tube in place relativeto the jacket. Preferably, the spacing material is a material which isable to flow between the disks and the jacket and then harden with lowshrinkage. A nonlimiting example of such a spacing material is EP30epoxy available from MasterBond Inc., 154 Hobart Street, Hackensack,N.J., U.S.A., 07601.

[0093] The present invention also contemplates that any type of agasketing material or shims known to one skilled in the art may be usedbetween the faces of adjacent superhard material disks to improve theirmating or to protect the superhard material and abrasive resistantmaterial pieces from damage during the press fitting operation. Suchgasketing material and shims may be used alone or in combination withother gasketing material or shims. Nonlimiting examples of suchgasketing materials include metallic gaskets. A nonlimiting example of amaterial suitable for such shims is soft copper. The thicknesses of thegasketing material and shims is preferably no greater than about 0.005inches (0.13 mm).

[0094] The present invention also comprises a tubular elongate superhardmaterial body, and methods for making same, wherein the tubular elongatesuperhard material body has at least one bore formed by EDM which issubstantially parallel to the longitudinal axis of the tubular elongatesuperhard material body. Such tubular elongate superhard material bodieshave a ratio of bore length to bore diameter of about 20 to about 400.The length of such a tubular elongate superhard material body is atleast about 0.24 inches (6 mm) and is preferably about 1 inch (25 mm).Likewise, the bore length of such a tubular elongate body is at leastabout 0.24 inches (6 mm) and is preferably about 1 inch (25 mm). Thebore diameter of such a tubular elongate superhard material body ispreferably in the range of from about 0.005 to about 0.19 inches (0.13to 4.8 mm) and more preferably in the range of from about 0.01 to about0.065 inches (0.25 to 1.7 mm). For example, referring to FIG. 15,tubular elongate superhard material body 400, has bore length 402 andbore diameter 404. Tubular elongate superhard material body 400 also hasbore 406 formed by EDM. Bore 406 is substantially parallel tolongitudinal axis 408 of tubular elongate superhard material body 400.

[0095] Such a tubular elongate superhard material may be made by firstforming an elongate superhard material body and then forming at leastone bore therein by EDM machining. Preferably, the elongate superhardmaterial body is cut by EDM from a solid sheet or disk of PCD. Such atubular elongate superhard material body may be used in an abrasivewater jet mixing tube as described herein or may be used in any otherapplication where a highly abrasion resistant passageway or conduitwould be beneficial (e.g., sand blast, grin blast, or water blastnozzles; paint nozzles; and powder spray nozzles such as powder spraydryer nozzles).

[0096] The present invention also comprises superhard material cylindershaving lengths of about 0.2 inches (5 mm) and diameters of about 0.2inches (5 mm) and either a straight passage or a conical passage or acombination of a straight passage and a conical passage, along theirlongitudinal centerlines, formed by EDM machining. Such superhardmaterial cylinders comprise a superhard material or a composite of asuperhard material bonded to another abrasion-resistant material. Wherea superhard material cylinder comprises a composite, preferably thenon-superhard material abrasion-resistant material consists of tungstencarbide.

[0097] An embodiment of a superhard material cylinder, first superhardcylinder 500, having a straight passage, first straight passage 502 isshown in FIG. 16A. An embodiment of a superhard material cylinder,second superhard material cylinder 504, having a conical section, firstconical section 506, is shown in FIG. 16B. An embodiment of a superhardmaterial cylinder, third superhard material cylinder 508, having acombination of a conical section, second conical section 510, and astraight section, second straight section 512, is shown in FIG. 16C. Anembodiment of a superhard material cylinder, composite cylinder 514,comprising a composite of superhard material 516 and anotherabrasion-resistant material 518, having a conical section, third conicalsection 520 is shown in FIG. 16D. Composite cylinder 514 preferablyincludes recess 522 for receiving a shoulder of a jacket, such as uppersection jacket shoulder 234 which is best seen in FIG. 13.

[0098] Where such a superhard material cylinder contains a straightpassage, either alone or in combination with a conical passage,preferably the aspect ratio of the cylinder length to the diameter ofthe passage is at least 3 to 1, and more preferably at least 6 to 1, andmost preferably at least 10 to 1, as these aspect ratios make thesuperhard material cylinders particularly useful in abrasive fluidcarrying applications, for example without limitation, as part of AWJmixing tubes.

[0099] Such a superhard material cylinder may be made by first forming acylindrical body and then EDM machining the desired passage orcombination of passages therein. Preferably, the cylindrical body is cutby EDM from a solid sheet or disk of PCD. Such a superhard materialcylinder may be used in an abrasive water jet mixing tube as describedherein or may be used in any other application where a highly abrasionresistant passageway or conduit would be beneficial (e.g., sand blast,grit blast, or water blast nozzles; paint nozzles; and powder spraynozzles such as powder spray dryer nozzles).

[0100] The patents and documents referred to herein are herebyincorporated by reference.

[0101] Having described presently preferred embodiments of the presentinvention, it is to be understood that the present invention may beotherwise embodied within the scope of the appended claims. Thus, whileonly a few embodiments of the present invention have been shown anddescribed, it will be obvious to those skilled in the art that manychanges and modifications may be made thereunto without departing fromthe spirit and scope of the present invention as described in theappended claims.

What is claimed is:
 1. An abrasive water jet mixing tube comprising alongitudinal bore lined with a monolithic superhard material.
 2. Theabrasive water jet mixing tube of claim 1 further comprising a durablematerial surrounding the superhard material substantially along thelength of the AWJ mixing tube.
 3. The abrasive water jet mixing tube ofclaim 2 wherein the durable material comprises a steel.
 4. The abrasivewater jet mixing tube of claim 2 wherein the durable material comprisesa cemented tungsten carbide.
 5. The abrasive water jet mixing tube ofclaim 1 wherein the superhard material has a thickness of at least about0.005 inches (0.13 mm).
 6. The abrasive water jet mixing tube of claim 1further comprising a tapered entryway connecting to the longitudinalbore.
 7. The abrasive water jet mixing tube of claim 6 furthercomprising a vapor deposition-deposited hard coating on a surface of thetapered entryway.
 8. The abrasive water jet mixing tube of claim 7wherein the hard coating is selected from the group consisting ofdiamond, titanium nitride, titanium carbide, titanium carbonitride,titanium aluminum nitride, aluminum oxide, and their combinations. 9.The abrasive water jet mixing tube of claim 1 further comprising anentryway piece bonded to an abrasive water jet body piece, the entrywaypiece having a superhard material formed on a tapered entryway and theabrasive water jet body piece having a longitudinal core lined with asuperhard material.
 10. The abrasive water jet mixing tube of claim 9wherein the superhard material formed on the tapered entryway has athickness of at least about 0.005 inches (0.13 mm).
 11. The abrasivewater jet mixing tube of claim 1 wherein the superhard material includespolycrystalline diamond.
 12. An abrasive water jet mixing tubecomprising an abrasive water jet body having a longitudinal bore linedwith a superhard material and further having a tapered entryway linedwith a superhard material.
 13. The abrasive water jet mixing tube ofclaim 68 wherein the superhard material lining the tapered entryway hasa thickness of at least about 0.005 inches (0.13 mm).
 14. The abrasivewater jet mixing tube of claim 68 wherein the bore and the taperedentryway are formed by EDM.
 15. An abrasive water jet mixing tubecomprising a flow passage formed by EDM machining in at least oneabrasion-resistant material piece, wherein at least part of the flowpassage has a lining comprising a superhard material.
 16. The abrasivewater jet mixing tube of claim 15 wherein the superhard materialincludes polycrystalline diamond.
 17. The abrasive water jet mixing cubeof claim 15 wherein the superhard material comprising the lining has athickness of at least about 0.005 inches (0.13 mm).
 18. The abrasivewater jet mixing tube of claim 15 further comprising a jacket and aspacing material wherein the spacing material is interposed between thejacket and at least one of said abrasion-resistant material pieces. 19.The abrasive water jet mixing tube of claim 18 wherein the jacketcomprises a material selected from the group consisting of a plastic anda metal.
 20. The abrasive water jet mixing tube of claim 18 furthercomprising a centering coupling wherein said centering couplinglongitudinally centers at least of said one abrasion-resistant materialpieces within said jacket.
 21. The abrasive water jet mixing tube ofclaim 15 wherein at least part of the flow passage is lined with anabrasion-resistant material other than a superhard material.
 22. Theabrasive water jet mixing tube of claim 15 further comprising a durablematerial laterally surrounding at least one of said abrasion-resistantmaterial pieces.
 23. The abrasive water jet mixing tube of claim 22wherein the durable material comprises cemented tungsten carbide. 24.The abrasive water jet mixing tube of claim 15 further comprising atapered entryway.
 25. The abrasive water jet mixing tube of claim 24wherein the tapered entryway includes a rim, and wherein said rimcomprises cemented tungsten carbide.
 26. The abrasive water jet mixingtube of claim 24 wherein the tapered entryway is formed in a pluralityof superhard material pieces.
 27. An abrasive water jet mixing tubecomprising: a) a plurality of components, and b) at least one connectionconnecting together said components; wherein each of said components hasa flow passage formed by EDM machining in at least oneabrasion-resistant material piece, and wherein the flow passage of aportion of at least one of said components has a lining comprising asuperhard material, and wherein the flow passage of each of saidcomponents is in fluid communication with the flow passage of each otherof said components.
 28. The abrasive water jet mixing tube of claim 27wherein said at least one connection includes a disconnectableconnection.
 29. The abrasive water jet mixing tube of claim 28 whereinsaid disconnectable connection is a threaded connection.
 30. Theabrasive water jet of claim 27 wherein at least one of said componentscomprises a tapered entryway.
 31. The abrasive water jet of claim 27wherein one of said components comprises an exit end of the abrasivewater jet and wherein at least part of the flow passage of saidcomponent comprising the exit end is lined with a superhard material.32. The abrasive water jet mixing tube of claim 27 wherein the superhardmaterial includes polycrystalline diamond.
 33. The abrasive water jetmixing tube of claim 27 wherein said superhard material comprising saidlining has a thickness of at least about 0.005 inches (0.13 mm).
 34. Theabrasive water jet mixing tube of claim 27 wherein at least one of saidcomponents further comprises a jacket and a spacing material, andwherein an abrasion-resistant material piece is disposed within saidjacket, and wherein said spacing material is interposed between saidjacket and said abrasion-resistant material piece.
 35. The abrasivewater jet mixing tube of claim 34 wherein said jacket comprises amaterial selected from the group consisting of a plastic and a metal.36. The abrasive water jet mixing tube of claim 34 further comprising acentering coupling wherein said centering coupling longitudinallycenters said abrasion-resistant material piece within said jacket. 37.The abrasive water jet mixing tube of claim 27 wherein at least part ofthe flow passage of at least one of said components has a lining of anabrasion-resistant material other than a superhard material.
 38. Theabrasive water jet mixing tube of claim 27 wherein at least one of saidcomponents comprises a tapered entryway.
 39. The abrasive water jetmixing tube of claim 38 wherein the tapered entryway includes a rim, andwherein said rim comprises cemented tungsten carbide.
 40. The abrasivewater jet mixing tube of claim 38 wherein the tapered entryway is formedin a plurality of superhard material pieces.
 41. A tubular elongatesuperhard material body having a bore formed by EDM machining, whereinsaid bore is substantially parallel to the longitudinal axis of thetubular elongate superhard material body, and wherein a ratio of thebore length to the bore diameter is in the range of about 20 to about400.
 42. The tubular elongate superhard material body of claim 41wherein the bore diameter is in the range of about 0.005 to about 0.190inches (0.13 to 4.8 mm).
 43. The tubular elongate superhard materialbody of claim 41 wherein the bore length is at least about 0.15 inches(4 mm).
 44. A superhard material cylinder having a diameter of about 0.2inches (5 mm) or less and a length of about 0.2 inches (5 mm) or moreand a straight passage formed by EDM machining, wherein a ratio of thelength of the superhard material cylinder to the diameter of thestraight passage is at least 3 to
 1. 45. The superhard material cylinderof claim 44 wherein said ratio of the length of the superhard materialcylinder to the diameter of the straight passage is at least 6 to
 1. 46.The superhard material cylinder of claim 44 wherein said ratio of thelength of the superhard material cylinder to the diameter of thestraight passage is at least 10 to
 1. 47. The superhard materialcylinder of claim 44 further comprising a composite, the compositecomprising a superhard material and tungsten carbide.
 48. A superhardmaterial cylinder having a diameter of about 0.2 inches (5 mm) or lessand a length of about 0.2 inches (5 mm) or more and a conical passageformed by EDM machining.
 49. The superhard material cylinder of claim 48further comprising a composite, the composite comprising a superhardmaterial and tungsten carbide.
 50. An abrasive water jet systemcomprising an abrasive water jet mixing tube, the abrasive water jetmixing tube having a longitudinal bore lined with and formed by EDM in asuperhard material.
 51. The abrasive water jet system of claim 50further comprising the use of abrasive particles selected from the groupconsisting of cubic boron nitride, diamond, and their combinations witheach other.
 52. The abrasive water jet system of claim 50 furthercomprising the use of abrasive particles having a hardness greater thanthat of garnet.
 53. The abrasive water jet system of claim 50 furthercomprising a booster pump.
 54. The abrasive water jet system of claim 50further comprising a filter.
 55. The abrasive water jet system of claim50 further comprising an intensifier pump.
 56. The abrasive water jetsystem of claim 50 further comprising high pressure piping.
 57. Theabrasive water jet system of claim 50 further comprising an AWJmachining head.
 58. The abrasive water jet system of claim 50 furthercomprising a computer.
 59. The abrasive water jet system of claim 50further comprising an AWJ machining head-moving mechanism.
 60. Theabrasive water jet system of claim 50 further comprising a collectiontank.
 61. The abrasive water jet system of claim 50 wherein thesuperhard material includes polycrystalline diamond.
 62. An abrasivewater jet system comprising an abrasive water jet mixing tube, saidabrasive water jet mixing tube including a flow passage formed by EDMmachining in at least one abrasion-resistant material piece, whereinsaid flow passage has a lining comprising a superhard material.
 63. Anabrasive water jet system comprising an abrasive water jet mixing tube,said abrasive water jet mixing tube comprising: a) a plurality ofcomponents, and b) at least one connection connecting together saidcomponents; wherein each of said components has a flow passage formed byEDM machining in at least one abrasion-resistant material piece, andwherein the flow passage of at least one of said components has a liningcomprising a superhard material, and wherein the flow passage of each ofsaid components is in fluid communication with the flow passage of eachother of said components.
 64. A method for producing an abrasive waterjet mixing tube, the method comprising the steps of: a) providing atleast one superhard material body; and b) EDM machining a longitudinalbore through the at least one superhard material body.
 65. The method ofclaim 64 wherein the at least one superhard material body has a firstend, the method further comprising the step of EDM machining a taperedentryway in the first end of the at least one superhard material body.66. The method of claim 65 further comprising the step of depositing ahard coating by vapor deposition on a surface of the tapered entryway.67. The method of claim 66 further comprising the step of selecting thehard coating from the group consisting of diamond, titanium nitride,titanium carbide, titanium carbonitride, titanium aluminum nitride,aluminum oxide, and their combinations.
 68. The method of claim 64further comprising the step of machining the at least one superhardmaterial body to adapt the at least one superhard material body to fitinto an abrasive water jet machining head.
 69. The method of claim 64wherein the superhard material includes polycrystalline diamond.
 70. Amethod for producing an abrasive water jet mixing tube, the methodcomprising the steps of: a) providing at least one superhard materialbody; b) surrounding the at least one superhard material body with adurable material to form an abrasive water jet mixing tube blank havinga superhard material core; and c) EDM machining a longitudinal borethrough the superhard material core of the abrasive water jet mixingtube blank.
 71. The method of claim 70 wherein the abrasive water jetmixing tube blank has a first end, the method further comprising thestep of EDM machining a tapered entryway in the first end of theabrasive water jet mixing tube blank.
 72. The method of claim 71 furthercomprising the step of depositing a hard coating by vapor deposition ona surface of the tapered entryway.
 73. The method of claim 72 furthercomprising the step of selecting the hard coating from the groupconsisting of diamond, titanium nitride, titanium carbide, titaniumcarbonitride, titanium aluminum nitride, aluminum oxide, and theircombinations.
 74. The method of claim 70 further comprising the step ofmachining the abrasive water jet mixing tube blank to adapt the abrasivewater jet mixing tube blank to fit into an abrasive water jet machininghead.
 75. The method of claim 70, wherein the at least one superhardmaterial body consists of a plurality of individual superhard materialbodies, each of the individual superhard material bodies having firstand second end faces such that the distance between the first and secondface comprises the length of the individual superhard material body, themethod further comprising the step of abutting at least one of saidfirst and second end faces of each said individual superhard materialbody against one of said first and second end faces of another of saidindividual superhard material bodies so that the plurality of individualsuperhard material bodies together form the superhard material core ofthe abrasive water jet blank.
 76. The method of claim 70 wherein thestep of surrounding the at least one superhard material body with adurable material to form an abrasive water jet mixing tube blank havinga superhard material core comprises bonding the at least one superhardmaterial body to the durable material.
 77. The method of claim 70wherein the step of bonding the at least one superhard material body tothe durable material includes using at least one of the group consistingof a brazing alloy and an adhesive to bond the at least one superhardmaterial body to the durable material.
 78. The method of claim 70wherein the durable material comprises a steel.
 79. The method of claim70 wherein the durable material comprises a cemented tungsten carbide.80. The method of claim 70 wherein the step of surrounding the at leastone superhard material body with a durable material to form an abrasivewater jet mixing tube blank having a superhard material core includesproviding at least one durable material body.
 81. The method of claim 80wherein the step of providing at least one durable material bodyincludes providing at least one durable material body having a cavityfor receiving the at least one superhard material body.
 82. The methodof claim 70 wherein the longitudinal bore has a superhard materiallining thickness of at least about 0.005 inches (0.13 mm).
 83. Themethod of claim 70 wherein the superhard material includespolycrystalline diamond.
 84. A method for producing an abrasive waterjet mixing tube, the method comprising the steps of: a) providing atleast one composite body, the at least one composite body having asuperhard material layer bonded to a cemented tungsten carbidesubstrate; b) providing at least one durable material body; c) bondingthe at least one composite body to the at least one durable materialbody so as to form an AWJ mixing tube blank having a superhard materialcore; and d) EDM machining a longitudinal bore through the superhardmaterial core of the AWJ mixing tube blank.
 85. The method of claim 84wherein the abrasive water jet mixing tube blank has a first end, themethod further comprising the step of EDM machining a tapered entrywayin the first end of the abrasive water jet mixing tube blank.
 86. Themethod of claim 85 further comprising the step of depositing a hardcoating by vapor deposition on a surface of the tapered entryway. 87.The method of claim 86 further comprising the step of selecting the hardcoating from the group consisting of diamond, titanium nitride, titaniumcarbide, titanium carbonitride, titanium aluminum nitride, aluminumoxide, and their combinations.
 88. The method of claim 84 furthercomprising the step of machining the abrasive water jet mixing tubeblank to adapt the abrasive water jet mixing tube blank to fit into anabrasive water jet machining head.
 89. The method of claim 84 whereinthe at least one superhard material body consists of a plurality ofindividual superhard material bodies, each of the individual superhardmaterial bodies having first and second end faces such that the distancebetween the first and second face comprises the length of the individualsuperhard material body, the method further comprising the step ofabutting a: least one of said first and second end faces of each saidindividual superhard material body against one of said first and secondend faces of another of said individual superhard material bodies sothat the plurality of the individual superhard material bodies togetherform the superhard material core of the abrasive water jet blank. 90.The method of claim 84 wherein the at least one durable material bodycomprises a steel.
 91. The method of claim 84 wherein the at least onedurable material body comprises a cemented tungsten carbide.
 92. Themethod of claim 84 wherein the longitudinal bore has a superhardmaterial lining thickness of at least about 0.005 inches (0.13 mm). 93.The method of claim 84 wherein the step of bonding the at least onecomposite body to the at least one durable material body so as to forman AWJ mixing tube blank having a superhard material core includes usingat least one of the group consisting of a brazing alloy and an adhesiveto bond the at least one superhard material body to the durablematerial.
 94. The method of claim 84 wherein the step of providing atleast one durable material body includes providing at least one durablematerial body having a cavity for receiving the at least one superhardmaterial body.
 95. The method of claim 84 wherein the step of providingat least one composite body includes providing a composite body havingsuperhard material formed in a groove of a cemented tungsten carbidesubstrate.
 96. The method of claim 84 wherein the superhard materialincludes polycrystalline diamond.
 97. A method for producing an abrasivewater jet mixing tube, the method comprising the steps of: a) providingan abrasive water jet body piece, the abrasive water jet body piecehaving a longitudinal bore lined with a superhard material; and b)bonding an entryway piece to the abrasive water jet body piece, theentryway piece having a superhard material formed on a tapered entryway.98. The method of claim 97 wherein the entryway piece includes a boresection extending from an apex of the tapered entryway.
 99. The methodof claim 97 wherein the superhard material formed on the taperedentryway has a thickness of at least about 0.005 inches (0.13 mm). 100.The method of claim 97 wherein the superhard material that lines theabrasive water jet body piece longitudinal bore has a thickness of atleast 0.005 inches (0.13 mm).
 101. The method of claim 97 wherein thestep of bonding an entryway piece to the abrasive water jet body pieceincludes using at least one of the group consisting of a brazing alloyand an adhesive to bond the entryway piece to the abrasive water jetbody piece.
 102. The method of claim 97 wherein the superhard materialincludes polycrystalline diamond.
 103. A method for producing an AWJmixing tube, the method comprising the steps of: a) providing anabrasion-resistant material piece comprising a superhard material; b)EDM machining a flow passage into said abrasion-resistant material pieceso that at least part of the flow passage has a lining comprising asuperhard material.
 104. The method of claim 103 wherein the step ofproviding an abrasion-resistant material piece includes providing aplurality of abrasion-resistant material pieces, the method furthercomprising the step of assembling together the plurality ofabrasion-resistant material pieces into an assembly prior to performingthe step of EDM machining a flow passage so that the step of EDMmachining a flow passage results in the flow passage being EDM machinedthrough the assembly.
 105. The method of claim 103 wherein the step ofEDM machining a flow passage includes forming a tapered entryway. 106.The method of claim 105 wherein the tapered passageway is formed in aplurality of superhard material pieces.
 107. The method of claim 103wherein the step of providing an abrasion-resistant material pieceincludes providing a composite consisting of a superhard material bondedto a cemented tungsten carbide, and wherein the tapered entryway has anouter rim, the method further comprising the step of forming a taperedentryway rim in the tungsten carbide.
 108. A method for producing an AWJmixing tube, the method comprising the steps of: a) providing anabrasion-resistant material piece comprising a superhard material; b)inserting said abrasion-resistant material piece into a jacket; and c)EDM machining a flow passage into said abrasion-resistant material pieceso that at least part of the flow passage has a lining comprising asuperhard material.
 109. The method of claim 108 wherein the step ofproviding an abrasion-resistant material piece includes providing aplurality of abrasion-resistant material pieces, the method furthercomprising the step of assembling together the plurality ofabrasion-resistant material pieces into an assembly prior to performingthe step of EDM machining a flow passage so that the step of EDMmachining a flow passage results in the flow passage being EDM machinedthrough the assembly.
 110. The method of claim 108 further comprisingthe step of interposing a spacing material between saidabrasion-resistant material piece and said jacket.
 111. The method ofclaim 108 further comprising the step of transversely centering saidabrasion-resistant material within said jacket with a centeringcoupling.
 112. The method of claim 108 wherein the step of EDM machininga flow passage includes forming a tapered entryway.
 113. The method ofclaim 108 wherein the tapered passageway is formed in a plurality ofsuperhard material pieces.
 114. The method of claim 108 wherein the stepof providing an abrasion-resistant material piece includes providing acomposite consisting of a superhard material bonded to a cementedtungsten carbide, and wherein the tapered entryway has an outer rim, themethod further comprising the step of forming a tapered entryway rim inthe tungsten carbide.
 115. A method for producing an abrasive water jetmixing tube, the method comprising the steps of: a) providing aplurality of components wherein each of said components has a flowpassage formed by EDM, and wherein the flow passage of at least one ofsaid components has a lining comprising a superhard material; and b)connecting said components together so that the flow passage of each ofsaid components communicates with the flow passage of each other of saidcomponents.
 116. The method of claim 115 wherein the step of connectingincludes disconnectably connecting at least one of said components to atleast one other of said components.
 117. The method of claim 116 whereinthe step of disconnectably connecting includes threadably connecting atleast one of said components to at least one other of said components.118. The method of claim 115 wherein one of said components comprises anexit end of said abrasive water mixing tube, and wherein the flowpassage of said component comprising the exit end has a liningcomprising a superhard material.
 119. The method of claim 115 whereinthe step of providing a plurality of components includes providing at acomponent having a jacket produced by substeps including: a) providingan abrasion-resistant material piece; b) inserting saidabrasion-resistant material piece into a jacket; and c) EDM machining aflow passage into said abrasion-resistant piece.
 120. The method ofclaim 119 wherein the step of providing component having a jacketfurther includes the substep of interposing a spacing material betweensaid abrasion-resistant material piece and said jacket.
 121. The methodof claim 115 wherein the step of providing a plurality of componentsincludes providing a component having a tapered entryway.
 122. Themethod of claim 121 wherein said tapered entryway is formed in aplurality of superhard material pieces.
 123. The method of claim 121wherein said tapered entryway has an outer rim, and wherein the step ofproviding a component having a tapered entryway includes the substepsof: a) providing a composite consisting of a superhard material bondedto a cemented tungsten carbide; and b) forming a tapered entryway rim inthe tungsten carbide.
 124. A method for making a tubular elongatesuperhard material body, the method comprising the steps of: a) formingan elongate superhard material body; and b) EDM machining at least onebore in the elongate superhard material body so that said bore issubstantially parallel to the longitudinal axis of said elongatesuperhard material body.
 125. The method of claim 124 wherein said borehas a length of at least about 0.24 inches (6 mm).
 126. The method ofclaim 124 wherein a ratio of the bore length to the bore diameter is inthe range of about 20 to about
 400. 127. The method of claim 124 whereinthe bore diameter is in the range of about 0.005 to about 0.190 inches(0.13 to 4.8 mm).
 128. The method of claim 127 wherein the bore diameteris in the range of about 0.1 to about 0.65 inches (2.5 to 17 mm).
 129. Amethod of using an abrasive water jet system, the method comprising thesteps of: a) providing an abrasive water jet mixing tube having alongitudinal bore lined with and formed by EDM in a superhard materialsb) providing abrasive particles; c) emitting the abrasive particles fromthe abrasive water jet mixing tube; and d) machining a workpiece withthe emitted abrasive particles.
 130. The method of claim 129 furthercomprising the step of selecting the abrasive particles from the groupconsisting of cubic boron nitride, diamond, and their combinations witheach other.
 131. The method of claim 129 wherein the workpiece comprisesa material having a hardness of about 9 or greater on the Mohs scale.132. The method of claim 129 wherein the workpiece comprises a materialselected from the group consisting of diamond and cubic boron nitride.133. The method of claim 129 wherein the superhard material includespolycrystalline diamond.
 134. A method of using an abrasive water jetsystem, the method comprising the steps of: a) providing an abrasivewater jet mixing tube, said abrasive water jet mixing tube including aflow passage formed by EDM machining in at least one abrasion-resistantmaterial wherein at least part of the flow passage has a liningcomprising a superhard material; b) providing abrasive particles; c)emitting said abrasive particles from said abrasive water jet mixingtube; and d) machining a workpiece with said emitted abrasive particles.135. The method of claim 134 wherein said workpiece comprises a materialhaving a hardness of about 9 or greater on the Mohs scale.
 136. Themethod of claim 134 wherein said workpiece comprises a material selectedfrom a group consisting of diamond and cubic boron nitride.
 137. Themethod of claim 134 wherein said superhard material includespolycrystalline diamond.
 138. A method of using an abrasive water jetsystem, the method comprising the steps of: a) providing an abrasivewater jet mixing tube; b) providing abrasive particles; c) emitting theabrasive particles from said abrasive water jet mixing tube; and d)machining a workpiece with said emitted abrasive particles; wherein theabrasive water jet mixing tube comprises a plurality of components andat least one connection connecting together said components, and whereineach of said components has a flow passage formed by EDM machining in atleast one abrasion-resistant material piece, and wherein the flowpassage of at least one of said components has a lining comprising asuperhard material, and wherein the flow passage of each of saidcomponents is in fluid communication with the flow passage of each otherof said components.
 139. The method of claim 138 wherein said workpiececomprises a material having a hardness of about 9 or greater on the Mohsscale.
 140. The method of claim 138 wherein said workpiece comprises amaterial selected from a group consisting of diamond and cubic boronnitride.
 141. The method of claim 138 wherein said superhard materialincludes polycrystalline diamond.
 142. The method of claim 138 whereinsaid at least one of connection includes a disconnectable connection.